Wyoming designated the American buffalo as official state mammal in 1985 (more correctly called bison). A bull buffalo can weigh over 1800 pounds and stand 6 foot tall at the shoulder. Buffalo once roamed the American prairie by the tens of millions and provided a way of life for the plains Indians. But European settlers hunted buffalo to the brink of extinction - it's estimated that between 300 - 500 animals remained when the federal government passed stricter game laws in 1889.

The buffalo is an inseparable part of American history; no other wild animal has played such a significant role in human affairs. The tribes of the American plains relied on bison for food, shelter, clothing, and as a powerful spiritual symbol. The American buffalo is also a state symbol of Kansas and Oklahoma.

Source:

General Wyoming Information: Wyoming.gov
Bison: Yellowstone National Park
Nature: American Buffalo: PBS
Bison (Bison bison): South Dakota Northern University

Links:

Bison: Yellowstone National Park Photos
State Animals - Mammals: 50 States List